1. Field of the Invention
The present invention generally relates to a method of forming a mask pattern on a substrate.
2. Description of the Related Art
Along with advances in a highly integrated circuit, wirings and separation widths required for the manufacturing process are being miniaturized. The micropattern is ordinarily formed by making a resist pattern using a photolithographic technique and etching various thin underlying films using the resist pattern as an etching mask. Therefore, in order to form the micropattern, the photolithographic technique is important. However, the micronization of recent semiconductor devices requires resolution better than the resolution limit of the photolithographic technique. Further, the resolution of the ArF immersion exposure technique which is presently a main stream of the micronization is said to reach its resolution limit in 4xnm generation. Therefore, in 3xnm generation achieving further minute micronization, a double patterning technique (Double Patterning: DP) is used. Therefore, a double patterning technique is being actively developed.
Such techniques of forming a pattern of a resolution limit or smaller resolution by the double patterning technique is described in, for example, Patent Document 1.
With Patent Document 1, a first resist opening pattern made of the first resist film is formed and a first hole pattern is formed in an underlying layer using the first resist opening pattern. Subsequently, a second resist opening pattern made of a second resist film is formed, and the second hole pattern is formed in the underlying layer using the formed second resist opening pattern. Such process is called a Lithography Etching Lithography Etching (LELE) process.
However, when the resist pattern is formed by double patterning such as the LELE process described above, the following problems may occur.
With the LELE process, after forming the first resist opening pattern by a coating and developing device, a first hole pattern is etched by an etching device to thereby form the first hole pattern. Thereafter, after the second resist opening pattern is formed by the coating and developing device, the subject undergoes etching again by the etching device to thereby form the second hole pattern. Therefore, there is a drawback that the number of processes increases.
In order to reduce the number of processes, a Lithography Lithography Etching (LLE) process may be used. With the LLE process, after the first resist pattern is formed, the second resist pattern is formed between the first resist patterns, and an underlying thin film is etched using the first resist pattern and the second resist pattern as the etching mask to thereby form a micropattern.
However, in the LLE process, when the first resist pattern including the first resist film is formed and then the second resist film is formed to make the second resist pattern, the first resist pattern may dissolve. Therefore, before forming the second resist film, a barrier layer may be formed on the first resist pattern or an insolubilization process may be performed.
Further, if a resist pattern having a line portion is formed, it is possible to reduce the width of the line portion by a slimming process using, for example, acid. However, when the resist pattern including the opening portions is formed, it is difficult to reduce the sizes of the opening portions by a slimming process or the like. Thus, it is difficult to form opening portions having sizes of the resolution of the photolithography machine or smaller.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2005-129761